The reason why cranial MRI is done for HER2(+) breast cancer is because this type of breast cancer has a higher risk of brain metastasis, and cranial MRI can be used to determine whether there is brain metastasis and the specifics of metastatic foci. 1. Judge whether there is brain metastasis: conventional CT examination has many limitations, such as insufficient resolution, poor soft tissue imaging, etc. Through cranial magnetic resonance, it can accurately judge the soft tissues in the cranium and brain, which is of great significance for clarifying whether there is brain metastasis of the tumor. 2. Determine the specific situation of metastatic foci: if brain metastasis occurs, through cranial magnetic resonance examination, it can determine the size, location, infiltration depth, and extent of metastatic foci, which is of great significance in guiding the follow-up treatment. Breast cancer is a relatively common malignant tumor in clinic, and the treatment pursues individualization, once it occurs, it should go to the hospital in time and be diagnosed and treated under the guidance of professional doctors.